There are a number of desirable characteristics of a denture fixative composition. One extremely desirable attribute is that it develops a high degree of tack upon contact with saliva in order that the dentures be held in place as soon as they are seated in the mouth. It is also highly desirable that the mucilage is spread over the denture-mucosa interface in order to effectively seal the denture in place and that the mucilages possess sufficient cohesive strength to withstand the stresses of mastication which act to rupture the seal and thus dislodge the denture. The denture fixative must also exhibit sufficient resistance to degradation under the extreme environmental temperature changes which occur in the oral cavity during such common actions as drinking coffee or other hot beverages.
Eberhard et al., in U.S. Pat. No. 2,997,399, teaches a dental fixative composition which is based on the use of hydroxyethyl cellulose and which also preferably contains methyl cellulose and polyacrylamide. The patent teaches that the hydroxyethyl cellulose should have an average degree of substitution of between 0.4 and 4.5 ethylene oxide groups per anhydroglucose unit. The patent further states that substantially equivalent results might be possible to obtain if only a minor proportion of the ethylene oxide groups are replaced with propylene oxide groups. However, the ethylene oxide cannot be replaced by propylene oxide at least as regards all or a substantial major portion of the ethylene oxide.
It has now been discovered that hydroxypropyl cellulose can be used in a denture fixative composition when combined with certain partially neutralized, optionally crosslinked polyacrylic acids or partially neutralized alkyl vinyl ether--maleic acid or anhydride copolymers, optionally crosslinked, or polyethylene oxide.
Numerous pharmaceutical formulations have employed polyacrylic acid and the use thereof has, in the past, been primarily directed to the exploitation of its thickening, suspending and emulsifying capabilities when the polymer is partially or wholly neutralized in amide or hydroxy solvents with an inorganic base, water soluble amine or some other combination thereof. In aqueous systems, the partially or wholly neutralized polyacrylic acid generates a gel which has low cohesive strength with a structure that may be easily ruptured when it is subjected to stresses such as those that occur during mastication.
U.S. Pat. No. 3,003,988 describes a dental fixative composition in which the dental fixative is a mixed partial salt containing calcium cations and alkali or quaternary ammonium cations of a lower alkyl vinyl ether-maleic anhydride type copolymer. The mixed salt copolymer is stated to be a water-insoluble but water-sensitized copolymer.
U.S. Pat. No. 3,736,274 teaches a dental fixative composition which contains a lower alkyl vinyl ether-maleic anhydride polymeric material, a polymeric N-vinyl lactam and a sodium carboxymethyl cellulose. The carboxymethyl cellulose prevents the maleic anhydride copolymer--N-vinyl lactam complex from completely precipitating when placed in water.
U.S. Pat. No. 3,868,432 teaches an anhydrous denture adhesive composition which is a mixture of a cationic polymeric component which is a copolymer of an acrylamide and an anionic synthetic gum component which can be a copolymer of maleic acid with vinyl lower alkyl ether.
The use of polyethylene oxide as a denture adhesive is described in U.S. Pat. No. 2,978,812.
It is the object of this invention to provide new and improved denture fixative compositions which exhibit sufficient cohesive strength to resist stresses such as those that occur upon mastication, which retain their fixative properties for prolonged periods of time and which exhibit resistance to the extreme environmental temperature changes encountered in use.
This and other objects of the invention will become apparent to those skilled in the art from the following detailed description.